Almost 150 Japanese lawmakers and a cabinet minister have visited the contentious Yasukuni shrine in Tokyo, a memorial to Japan's 2.5 million dead in World War II. This precedes Barack Obama's arrival in Tokyo.

The Yasukuni shrine honors Japan's estimated 2.5 million war dead, mostly ordinary soldiers or civilians, but also includes the names of people convicted of war crimes after Japan's August 1945 surrender. The accompanying war museum and its portrayal of Japan's role in the Second World War is also sometimes criticized as unbalanced. For neighbors in Asia like China and South Korea, occupied by Japanese forces during the Second World War, such visits are a strain on ties with Japan.

Yoshitaka Shindo, minister for internal affairs and communications, was the highest-ranking politician among Tuesday's visitors, making his second trip to Yasukuni in 10 days. Shindo told reporters that he had attended as a private citizen.

Abe visited Yasukuni for the first time as prime minister in December

Prime Minister Shinzo Abe, who earned a mild US rebuke in December when he visited the Yasukuni shrine, did not attend this week but on Monday donated a tree to the facility. China described this gesture, too, as a "slap in the face" for US President Barack Obama, who arrives in Japan on Wednesday. His next stop will be the South Korean capital Seoul.

Abe's December 26 trip to Yasukuni had prompted the US to issue a statement saying it was "disappointed that Japan's leadership has taken an action that will exacerbate tensions with Japan's neighbors."

Japan and China's relations have been frayed in recent months, mainly by a territorial dispute over islands in the East China Sea claimed by both countries.